The present invention relates to a wave-shaper device.
Wave-shaper devices are commonly used in several applications, for example in a transmitter of a control system for air-bags. A wave-shaper device outputs a periodic analog signal, typically a pseudo-sinusoidal voltage; the analog signal is used to drive a power device (such as a current modulator in the aforementioned transmitter), which is coupled to the wave-shaper device.
The power device is subject in use to a noise, which is propagated to the wave-shaper device (coupled to the power device) and therefore affects its operation. For example, the noise may alter the value of reference quantities (voltages or currents) used by the wave-shaper device, thereby modifying the frequency of the analog signal.
The solutions known in the art for preventing this problem employ extremely complex and expensive circuitry. Moreover, filtering capacitors with a high capacitance are also generally used; however, these components increase the cost and size of the whole system in which the wave-shaper device is included.
An embodiment of the present invention is a wave-shaper device having an output terminal for providing a first periodic analog signal with a first frequency, the wave-shaper device including an oscillator having an output terminal for providing a second periodic analog signal with a second frequency which is multiple with an even factor of the first frequency, and means for obtaining the first analog signal from the second analog signal.
Other embodiments of the present invention provide a transmitter comprising this wave-shaper device, a control system for air-bags comprising the transmitter, and a corresponding method of generating a periodic analog signal.